PHOSPHOINOSITIDE KINASES IN CHICK BRAIN AND SCIATIC NERVE, A DEVELOPMENTAL STUDY

Phosphatidylinositol kinase and diphosphoinositide kinase activities were measured in homogenates of brain and sciatic nerve of developing chick embryos and chicks. Characteristics of the chick nervous system enzymes were similar to those reported for rat brain. Diphosphoinositide kinase was inhibited by high concentrations of ATP and by low concentrations of triphosphoinositide. Both activities were greatly enhanced by the non-ionic detergent, Cutscum, and the ratio of detergent to protein in the reaction mixture was important. Optimum phosphatidylinositol kinase activity required a ratio of 7 : 1 for both tissues. The optimum ratio for diphosphoinositide kinase was 3:1 for nerve homogenates and 0.6:1 for brain. Cutscum increased the concentration of diphosphoinositide that is required for maximum diphosphoinositide kinase activity. Developmental changes were the same for both kinase activities, which were low in unmyelinated brain and sciatic nerve. The activities correlated with the concentration of polyphosphoinositides in chick brain where they increased 4-5 fold during the period of active myelination and remained high in the mature brain. The kinase activities correlated with the rate of triphosphoinositide deposition in sciatic nerve. Following a 2-3 fold increase during the initial phase of myelination the activities declined to values as low as those of embryonic nerve.     

Biosynthesis of Choline and Ethanolamine Phospholipids in Crithidia fasciculata*

The incorporation of radioactivity from [1,2-³⁴C]choline, [1,2-³⁴C]ethanolamine, [3-¹⁴C]serine and [methyl-¹⁴C]methionine into lipids was studied in growing cultures of Crithidia fasciculata. Lecithin was formed both from choline and by the methylation of phosphatidylethanolamine. Mono- and dimethylphosphatidylethanolamines were present in no more than trace amounts. Growth of the protozoa in media containing choline (1 mM) did not decrease synthesis by the methylation pathway. Phosphatidylethanolamine was formed from ethanolamine. Radioactivity from serine also was present in both phosphatidylethanolamine and lecithin; however, the presumed intermediate, phosphatidylserine, could not be detected.     

Diagnosis of Metastatic Pleomorphic Giant Cell Carcinoma of the Pancreas Using Fine Catheter Aspiration Cytology

The value of fine catheter aspiration cytology in the diagnosis of metastatic tumours is illustrated by a case of pleomorphic giant cell carcinoma of the pancreas which had metastasized to the peritoneal cavity. The finding of unequivocal malignant cells obviated the need for further diagnostic procedures. Electron microscopy and immunostaining further substantiated the light microscopic cytodiagnosis and identified the tumour type and source of the primary tumour. Furthermore, subsequent cell block preparation from the aspirated material demonstrated the histological features of this tumour.     

Growth and yield of maize at different altitudes in Rhodesia

A late (SR 52) and an early (N × K) variety were grown, with irrigation, on well fertilized soil at three sites, Chiredzi (altitude 420 m), Henderson (1260 m) and Grasslands (1620 m). Mean incoming radiation was similar at all sites, while mean temperature decreased as altitude increased. Final total and grain dry weights were greatest at Henderson, and those of SR 52 exceeded those of N × K, although not greatly at Chiredzi. Initially, leaf area index (L) decreased with increase in altitude, but plants flowered later as altitude increased, and L at the time of flowering was greatest at Henderson. L at flowering was greater in SR 52 than in N × K, though only slightly so at Chiredzi. Leaves withered sooner after flowering at Chiredzi and Grasslands than at Henderson, but leaves of the two varieties withered at about the same time after flowering at each site. During most of the vegetative phase the efficiency of the leaves and crop growth rate (C) increased with decrease in altitude, and were greater in N × K than in SR 52. More dry matter was accumulated after flowering at Henderson than at the other sites, and more by SR 52 than by N × K at Henderson and Grasslands, but not at Chiredzi. Leaf area duration (D) after flowering was greater at Henderson than elsewhere, and greater in SR 52 than in N × K, except at Chiredzi. After flowering leaf efficiency (dry weight increase ÷D) was least at Henderson and greatest at Grasslands, but differed little between varieties at each site. The fraction in the grain of the dry matter accumulated after flowering decreased with increase in altitude and was greater in SR 52 than in N × K.